There is a known distribution system that includes a transmission device and a plurality of reception devices configured to be capable of communicating with each other and allows the plurality of reception devices to synchronously reproduce content. As one of this type of distribution systems, a distribution system described in Patent Document 1 matches time of a clock disposed to each of the plurality of reception devices with time of a reference clock. Moreover, the transmission device transmits reproduction start time, which is time that the reception device starts reproduction of content, to each reception terminal.
Then, the transmission device transmits content data representing content (video, audio, etc.) to each of the reception devices. Each of the reception devices stores received data among the content data into a storage device (a buffer) while receiving the content data. Moreover, each of the reception devices starts reproduction of content based on the stored data at the reproduction start time. As a result, it is possible to match the positions to reproduce the content with each other among the plurality of reception devices.
Further, a distribution system described in Patent Document 2 is a system that allows a plurality of reception devices to synchronously reproduce content even if time to start reproduction of the content varies depending on the reception device. In this distribution system, while a first reception device is reproducing content, a second reception device estimates a time required to start reproduction of the content and determines reproduction start time based on the estimated time. Then, the second reception device transmits the determined reproduction start time to the transmission device.
Consequently, the transmission device transmits, to the second reception device, content data to be transmitted to the first reception device at and after the reproduction start time. Then, the second reception device starts reproduction of content based on the stored data at the reproduction start time. As a result, it is possible to match positions to reproduce content with each other between the first reception device and the second reception device.
[Patent Document 1] Japanese Unexamined Patent Application Publication No. 2005-191786
[Patent Document 2] Japanese Unexamined Patent Application Publication No. 2007-13705
While the reception device is receiving content data, the amount of data that the reception device receives from the transmission device per unit time (i.e., a communication speed) varies depending on the status of use of a communication line, and so on. Therefore, when the communication speed becomes extremely low, there is a case that the data amount of content data stored in the storage device of the reception device does not reach a sufficient amount by the reproduction start time. In such a case, there is a fear that the reception device cannot start reproduction of content at the reproduction start time.
In order to deal with this, it can be considered to configure a distribution system to change a code rate of content data to be transmitted based on an available reproduction time, which is a time that it is possible to reproduce content based on content data stored in the storage device of the reception device.
However, during a period between start of reception of content data by the reception device and reproduction start time, the available reproduction time gradually increases from 0. Therefore, in a case that the code rate is determined based on only the available reproduction time, there is a fear that the code rate is set to be extremely small immediately after the reception device starts reception of the content data and, on the other hand, the code rate is set to be extremely high immediately before the reproduction start time.
Further, such a problem arises not only in a distribution system in which a plurality of reception devices synchronously reproduce content but also in a distribution system in which one reception device starts reproduction of content at set reproduction start time.